1. Field of the Invention
The invention relates generally to a filter element, and more particularly, to a filter element having a corrugated or embossed composite nonwoven filter media.
2. Discussion of the Prior Art
Some known filter media composite constructs incorporate a wet-laid paper making process to produce the substrate, and an electro-spun technology to deposit a lightweight nanofiber coating on one or both sides of the filter media substrate. Typically the media substrate has a basis weight of 100-120 grams per square meter (g/m2), and the nanofiber layer has a basis weight of 0.5 g/m2 or less.
It is known that some lightweight nanofiber layers may be subject to high mechanical stress applications. Such applications may be of interest for nanofiber layers formed from fibers with diameters less than 500 nanometer (nm), and more typically, 100 nm. Also, known electro-spun nanofiber layers are two dimensional in structure when attached to a substrate, as shown in FIG. 1, with a single fiber layer in thickness. It is known that there may be fiber shedding where the nanofibers are shed from the filter media because of relatively weak attraction bonds between the nanofibers and the base media for conventional electro-spun fibers that rely on polarity attraction forces. Such may have some reduced filtration performance aspects.
Filter media composite constructs may be used to provide for clean air provision to various devices. Such devices may include turbine blades. Typical, known filter media may have a new or clean operating efficiency providing for around 55% of capture of 0.3-0.4 μm particles, at a pressure drop typically greater than 7.0 mm H2O, when tested in accordance with the ASHRAE 52.2-1999 test procedure at the known operating flow rate.
Turning to example device that contain turbine blades, it is logical to try to maintain the turbine blades clean. One current procedure for cleaning turbine blades requires taking the turbine off-line at periodic intervals to water wash the blades clean. Turbine down time may be expensive because the turbine is not operating and therefore, power generation is curtailed. It would be desirable to provide a higher efficiency filter media than the known filter media to reduce or eliminate turbine down time to clean the turbine blades.
The best in performance of current technology is rated at F-9, using standard wet laid base media coated with an electrospun fiber surface layer. Too date the maximum efficiencies have been limited by the electrospinning process to around a maximum of 75% efficiency when challenged with 100% 0.30 micron DOP particles. This has been achieved with either heavy layers of elecrospun fibers on one surface of a wet laid base media or the use of a nanofiber layer on both surfaces of the base media.